Coal Discards and Sewage Sludge Derived-Hydrochar for HIV Antiretroviral Pollutant Removal from Wastewater and Spent Adsorption Residue Evaluation for Sustainable Carbon Management

Abstract

The effects of various parameter interactions on the textural structure of hydrochars produced via hydrothermal (HTC) and co-hydrothermal (Co-HTC) treatments of coal discards and sewage sludge (wastes), as well as the subsequent use of the hydrochars (HCs) synthesized for HIV drug (nevirapine and lamivudine) removal from wastewater, were investigated in this study. The HTC and Co-HTC process improved the carbon content of the raw material by 13.47%, 7.08%, and 30.65% for hydrochar coal tailing (HCT), hydrochar coal slurry (HCS), and hydrochar from coal–sewage blend (HCB), respectively. The Co-HTC-derived HCB had a high SBET of 20.35 m2/g and pore volume of 0.38 cm3/g, leading to significant adsorptive reductions of nevirapine (NEV) and lamivudine (LAM) (97.19% and 93.32%, respectively). HCT and HCS displayed high NEV and LAM adsorption capacities (50 mg g−1, 42 mg g−1 and 52 mg g−1, 41 mg g−1), respectively, despite being less effective than HCB (53.8 mg g−1, 42.8 mg g−1). In addition, the use of spent adsorption residues for energy storage applications was investigated further. The findings showed that spent adsorption residues are an effective carbonaceous material precursor to produce electrical double-layer capacitors (EDLCs).